The long-term objective of the research proposed is to better understand the relationship, if any, between cardiovascular reactivity to stress and predisposition for the development of coronary heart disease. The blood pressure and heart rate response of coronary-prone (Type A) and coronary-resistant (Type B) adults to (a) standardized laboratory stressors and (b) life stress associated with routine daily living will be studied. The entire laboratory testing and ambulatory monitoring procedure will be repeated two months after the first observation period. The primary aim is to determine the reproducibility (test-retest reliability) of cardiovascular stress responses observed in the laboratory and in the real-life situation, as well as the relationship between the two kinds of stress responses ('external validity' of laboratory stressors). The external validity of standardized stressors is important because available evidence suggests that it is the overall pressure to which the circulation is exposed as the result of the stresses of routine daily living which is associated with eventual target organ damage. The level at which blood pressure and heart rate are maintained during exposure to the recurring stresses of daily life will be estimated by 24-hour monitoring of ambulatory blood pressure and heart rate using an automatic noninvasive portable recorder worn by the subject. The standardized laboratory stressors will be mental arithmetic, reaction time, mirror drawing, cold pressor, isometric handgrip, and competitive social interaction. A pilot experiment will estimate the cardiovascular effect of the ambulatory monitoring procedure itself.